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Grape Cob Brown Blight and Its Control Techniques
Grape brown ear blight is a newly identified disease affecting grapevines, which has become increasingly severe in regions such as Liaoning, Shandong, and Hunan in recent years. In some vineyards in Liaoning, over 50% of the plants are infected, with a significant yield loss of up to 20% to 30%. This disease poses a serious threat to grape production and requires immediate attention.
Symptoms of the disease typically appear on young grape clusters. The early signs include browning and wilting of the panicle branches and cobs, which eventually dry out and turn dark brown. Affected parts may develop black mold, especially in wet conditions, which is caused by the pathogen's spores. In advanced stages, the dried branches often fall off, and small, dark brown spots (about 2 mm in diameter) may appear on the developing fruit. These lesions remain on the outer layer of the fruit and may develop into scab-like formations as the fruit grows. However, they usually do not significantly affect the fruit’s development. The disease can also infect the flower petals when the flowers are open.
Environmental factors play a major role in disease occurrence. The disease tends to be most severe from late April to May, during the flowering stage of the grapes, especially when temperatures are low and rainfall is heavy. Additionally, there are differences in resistance among grape varieties. Varieties like Jufeng are highly susceptible, while Black Olin and Red Banana show slightly less damage. Older vines tend to suffer more than younger ones (2-3 years old). Vineyards located in low-lying areas or surrounded by buildings experience higher incidence rates, whereas those in open, well-ventilated, and well-lit areas have fewer cases. The disease is more prevalent in northern regions compared to southern ones.
To manage this disease effectively, several control measures can be implemented. Before bud break, spraying with 3–5 degrees of lime sulfur or a 0.3% sodium pentachlorophenol solution helps eliminate overwintering pathogens and protect the buds. During the flowering period, applying 50% carbendazim wettable powder diluted 1000 times or thiophanate-methyl at 500–800 times provides good control. Improving orchard management, reducing humidity, and planting resistant varieties are also essential strategies for long-term disease prevention.